1) Field of the Invention
The present invention relates to a stent and, in more particular, to a stent that is capable of being positioned within a lumen of the esophagus.
2) Description of Related Art
Stents are devices that are inserted into body lumina such as vessels or passages to keep the lumen open and prevent closure due to a stricture, external compression, or internal obstruction. In particular, stents are commonly used to keep blood vessels open in the coronary arteries, and they are frequently inserted into the ureters to maintain drainage from the kidneys, the bile duct for pancreatic cancer or cholangiocarcinoma, or the esophagus for strictures or cancer. Vascular as well as nonvascular stenting has evolved significantly; unfortunately, there remain significant limitations with respect to the effectiveness of the stents following implantation into a patient's esophagus.
Stenting of the esophagus has proven to be challenging. The esophagus is a muscular lumen that is about ten inches long and extends from the hypopharynx to the stomach. The esophageal lumen is subject to wavelike contractions known as peristalsis, which pushes food down through the esophagus to the stomach. The esophagus is subject to complications that may require stenting, surgical repair, or dilatation. For example, a benign or malignant tumor may form in the esophagus that may be unable to be surgically removed, necessitating stenting or further surgical repair to prevent the lumen from constricting further. Left untreated, the tumor may lead to dysphagia, resulting in difficulty in swallowing.
Conventional stents utilized for the esophagus have significant drawbacks. Because the esophagus is very soft and flexible compared to other lumina, preventing migration of the stent is problematic. In particular, the esophagus frequently changes size and position, which causes complications for typical stents. For instance, a stent having a constant diameter along its entire axial length will have a tendency to migrate as the esophagus expands. The stricture is narrower than the lumen located proximally and distally of the stricture, and the stent is longer than the length of the stricture such that the portions of the stent proximately and distally of the stricture do not help prevent the stent from migrating. Therefore, there is an increased possibility that the stent will migrate within the lumen.
Moreover, the esophageal lumen is muscular and its wavelike contractions generally travel from its proximal end to its distal end resulting from an impulse applied at one side of the lumen wall. Due to the actions of the lumen, flexible stents have been designed to mimic the movement of the lumen. However, flexible stents may be prone to infolding or kinking, effectively occluding one or both of the openings of the stent. Furthermore, providing more rigid stents increases the risk of damage to the lumen of the esophagus, such as by damaging the blood vessels lining the lumen. Rigid stents are also typically more prone to migration.
Thus, there is a need in the industry for an esophageal stent that is capable of conforming to a lumen and maintaining the opening through a stricture. In addition, there is a need for a esophageal stent that reduces migration and the possibility of obstruction of the stent openings.